Brake Pump Cycling Randomly

I just recently noticed that when I push my brake pedal down I can hear/feel my brake/ABS pump activating. I don't recall this being normal as I've owned this truck for over 2 years now. Am I going crazy? It hasn't affected driving or braking at all. It happens when in motion or stopped. When in park it seems to cycle every 3rd push of the pedal or so

I bled my brakes using the brake pump (key in ON position) about 2-3 weeks ago, since then I've gotten an alignment and adjusted my rear drums. Could I have let some air into the calipers which is causing the pump to activate and am just now noticing?

 

You bled your brakes? Did you happen to run your master cylinder empty? You may need to take it to the dealer or somewhere and get the abs system bled. Typically they have to remove the brake master cylinder off the vehicle and bench bleed. Let me see if I can find exactly what you need to ask for at the shop as they typically wont do it unless you ask for this specific verbiage. Stand by.

-J

 

You need to cycle the ABS pump through Techstream. You can either buy a version on Amazon and do it yourself or take it to the dealer. You can't bleed your pump without using the onboard ABS system. Toyota Techstream has this function built into it. You manually bleed the Passenger Front and Passenger Rear brake and then bleed the ABS pump via software.

DIY version:

https://www.amazon.com/gp/product/B07JWBK4G9/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

 

Yup, this. Your ABS solenoids need to be bench bled. Meaning that the system needs to be forced to cycle continuously to bleed the air out. This can only be done with the above software.

-J

 

I was super careful not to let the MC reservoir run even remotely low, I can't picture the pump needing to be bled. Would air in a caliper cause this as well?

 

no, the ABS ECU manages the pump. What air you leave in the lines is your problem. That is why the procedure is to bleed the passenger side front and rear and then cycle the computer. It will cycle out any air from the driver side during the procedure.

 

Thanks for that, do you have a PDF of the procedure?

Hypothetically speaking, if there was air in a line wouldn't the ABS pump detect this when pressure is applied to the brake pedal and begin to cycle? Just like it would if the bleeder was opened and the brake pedal is pressed?

 

My understanding is the abs pump only detects air in the pump which triggers the automatic bleed procedure. It triggers the ABS to actuate based upon the wheel speed sensor pulse rings and not a reduction in line pressure.

A brake distribution valve, typically found after the master cylinder, will shift pressure between front and back, as an example, if there is enough air in the line or in the event of a breach in the brake line.

The procedure is outlined in the tech stream software as you run the check on the ABS system. It tells you when to apply speed bleeders and where, then close the system and apply the brake while it cycles the pump. I’m sorry but I don’t have any screenshots.